Question

In a microscope the focal lengths of two lenses are 1.5 cm and 6.25 cm. If an object is placed at 2 cm from objective and final image is formed at 25 cm from eye – lens, the distance between two lenses is –

• A. 6 cm
• B. 7.75 cm
• C. 9.25 cm
• D. 11 cm

Answer 1

Answer: (D)

11 cm

Answer 2

For objective lens

$\frac { 1 } { 1.5 }$ = – $\frac { 1 } { - 2 }$ Ž v₀ = 6cm

For eye lens :

$\frac { 1 } { - 25 }$ – = $\frac { 1 } { + 6.25 }$

Ž u_e = 5cm

\ L = v₀ + u_e = 6 + 5 = 11 cm